French to English Tech/Engineering Nuclear Eng/Sci

Not much context I'm afraid as it forms part of a list.
The document I'm translating relates to the removal and replacement of a vessel closure head in a Nuclear Power Plant and this appears to be one of the components.

There's a list that goes like this:
Passerelle à câbles
**BR**Dalle 20m
Enveloppes de ventilation
**BR**0m

Can anyone shed any light on what BR might mean?

Thanks